How can I block out spaces in my crossword?

In the United States,
it's typical for multiple-word answers in crossword puzzles to be present
without spaces or any other separators. For example, GIANTCOW.
However, in some other countries, it's common for there to be a space in the
crossword grid to represent the space between the two words. For
example, GIANT COW, where the space would be indicated in the empty grid by
a partially-shaded box.

EclipseCrossword will allow you to use spaces in your words, so you can
choose between GIANTCOW and GIANT COW as appropriate. However,
spaces will just appear as regular empty boxes in a printed crossword puzzle
if you include them, and do not get any special treatment or shading.
Also, if you have the option turned on to print the number of letters in
each word after each clue, it will treat the spaces as letters, such as
"Humongous bovine (9)" as opposed to "Humongous bovine (5, 3)." So, we
recommend that you avoid including spaces in your words.

If you do decide to include spaces anyway, we suggest that you mark them in
some way manually after you print, by adding slashes or an X in the
appropriate places in your puzzle.